[zeromq-dev] zeromq performance

Paul Phillips paul at marketgridsystems.com
Mon Jun 9 15:24:00 CEST 2014


I can set my processes and threads to use the same CPU (and I can then duplicate my test).

One thing that I am interested to know more about though is the ZMQ_AFFINITY option.  It seems to me that once zmq creates its own thread (or threads), I can’t control which CPU core the zmq thread(s) runs on.  I believe that ZMQ_AFFINITY will let me lock a socket to a particular zmq thread but the zmq thread itself could wander around over the CPU cores.  Even though I assign the parent application process (or thread) to a particular core, I believe that the zmq thread that is spawned would not be bound to that core.  Is that correct?

Regards, Paul Phillips
Director, MarketGrid Systems Pty Ltd
t: +61 419 048 874
e: paul at marketgridsystems.com



On 9 Jun 2014, at 11:18 pm, Charles Remes <lists at chuckremes.com> wrote:

> Yes, the default is one I/O thread. This assumes you are using IPC and/or TCP for transport. If you use INPROC then I think it skips the creation of any I/O thread.
> 
> So, to duplicate your test using the ZMQ_AFFINITY socket option, you would want to specify that all endpoints are using the same CPU.
> 
> cr
> 
> On Jun 7, 2014, at 12:00 PM, Paul Phillips <paul at marketgridsystems.com> wrote:
> 
>> I can look at this.  However, at this point, I am calling zmq_ctx_new() and not setting any options, so I assume that for each of my processes I only have one zmq I/O thread for all its sockets and connections.  Is that correct?
>> 
>> Regards, Paul Phillips
>> Director, MarketGrid Systems Pty Ltd
>> t: +61 419 048 874
>> e: paul at marketgridsystems.com
>> 
>> 
>> 
>> On 8 Jun 2014, at 2:55 am, Charles Remes <lists at chuckremes.com> wrote:
>> 
>>> This is a very interesting result. It’s probably worthwhile to add this to the FAQ.
>>> 
>>> It would be interesting to test this scenario with the ZMQ_AFFINITY option for zmq_setsockopt. If you have a chance, could you let us know if setting the I/O thread affinity results in a similar performance difference?
>>> 
>>> cr
>>> 
>>> On Jun 7, 2014, at 7:44 AM, Paul Phillips <paul at marketgridsystems.com> wrote:
>>> 
>>>> I have tracked down the source of this “problem”.  It turns out that the running multiple local-remote sets is not the key, it is actually related to what processor core things are running on.  If the local_lat and the remote_lat run on the same core then the comms is very fast (whether ipc or tcp).  If they are on separate cores, the comms is slower.  When I ran multiple sets, it just turned out that for some reason, the second local and remote set would be on the same core.  I can replicate the whole thing using taskset to force local_lat and remote_lat either to different or the same cores.
>>>> 
>>>> I have pasted my results from two runs, the first using separate cores and the second using the same core and the results are very different - 25 micros latency vs 7 micros latency (I have printed a couple of extra things at the end and renamed the executables to xlocal_lat and xremote_lat but they are the same code from the perf directory in the distribution of 4.0.4).
>>>> 
>>>> (MarketGrid)[Paul at CentOS65-Dev tmp]$ taskset -c 0 ./xlocal_lat ipc://testport2 100 100000 &
>>>> [1] 3566
>>>> (MarketGrid)[Paul at CentOS65-Dev tmp]$ taskset -c 1 ./xremote_lat ipc://testport2 100 100000 &
>>>> [2] 3578
>>>> (MarketGrid)[Paul at CentOS65-Dev tmp]$ message size: 100 [B]
>>>> roundtrip count: 100000
>>>> average latency: 25.421 [us]
>>>> elapssed: 5084170
>>>> throughput: 19668
>>>> 
>>>> [1]-  Done                    taskset -c 0 ./xlocal_lat ipc://testport2 100 100000
>>>> [2]+  Done                    taskset -c 1 ./xremote_lat ipc://testport2 100 100000
>>>> (MarketGrid)[Paul at CentOS65-Dev tmp]$ 
>>>> (MarketGrid)[Paul at CentOS65-Dev tmp]$ 
>>>> (MarketGrid)[Paul at CentOS65-Dev tmp]$ taskset -c 0 ./xlocal_lat ipc://testport2 100 100000 &
>>>> [1] 3581
>>>> (MarketGrid)[Paul at CentOS65-Dev tmp]$ taskset -c 0 ./xremote_lat ipc://testport2 100 100000 &
>>>> [2] 3584
>>>> (MarketGrid)[Paul at CentOS65-Dev tmp]$ message size: 100 [B]
>>>> roundtrip count: 100000
>>>> average latency: 7.016 [us]
>>>> elapssed: 1403130
>>>> throughput: 71269
>>>> 
>>>> [1]-  Done                    taskset -c 0 ./xlocal_lat ipc://testport2 100 100000
>>>> [2]+  Done                    taskset -c 0 ./xremote_lat ipc://testport2 100 100000
>>>> (MarketGrid)[Paul at CentOS65-Dev tmp]$ 
>>>> 
>>>> Regards, Paul Phillips
>>>> Director, MarketGrid Systems Pty Ltd
>>>> t: +61 419 048 874
>>>> e: paul at marketgridsystems.com
>>>> 
>>>> 
>>>> 
>>>> On 7 Jun 2014, at 6:17 pm, Pieter Hintjens <ph at imatix.com> wrote:
>>>> 
>>>>> How many messages are you sending? There will be a start-up cost that
>>>>> can be disproportionate if you send only a few messages.
>>>>> 
>>>>> On Sat, Jun 7, 2014 at 6:54 AM, Paul Phillips
>>>>> <paul at marketgridsystems.com> wrote:
>>>>>> Hi.  I have an interesting scenario when testing zeromq 4.0.4 on CentOS 6.5.
>>>>>> When I run local_lat and remote_lat using ipc, I get a latency of around 30
>>>>>> micros.  However, if I run them once in the background with a large round
>>>>>> trips setting (so they keep running for a long time) and then run a second
>>>>>> set, the second set always returns a latency of around 7 micros.  Basically,
>>>>>> once I have one lot of stuff running in the background, subsequent stuff
>>>>>> always seems to run much faster.  Is there any known explanation for this
>>>>>> behaviour?
>>>>>> 
>>>>>> Regards, Paul Phillips
>>>>>> 
>>>>>> Director, MarketGrid Systems Pty Ltd
>>>>>> t: +61 419 048 874
>>>>>> e: paul at marketgridsystems.com
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
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